The lack of the BindingExpression type and related functionality in WinRT is a serious issue to anyone trying to create custom controls. Hopefully this issue will be resolved post-beta.

Sadly, the only information I’ve been able to find on this topic from Microsoft is the suggestion to use LostFocus event handlers instead of binding. Obviously that’s a pretty useless workaround when trying to create a custom control

I started writing a data binding engine for Android (because they don’t have one at all). It would be a serious shame if we’re forced to write a data binding engine for XAML in WinRT just to be able to implement basic custom control concepts…